Re: [PATCH v3] thermal: rockchip: make temperature reporting much more accurate

[Caesar Wang]

å 2015å01æ22æ 12:25, Daniel Kurtz åé:
> On Thu, Jan 22, 2015 at 12:21 PM, Caesar Wang
> <caesar.wang@xxxxxxxxxxxxxx> wrote:
> > å 2015å01æ22æ 12:01, Daniel Kurtz åé:
> >
> > > On Thu, Jan 22, 2015 at 1:29 AM, Caesar Wang <wxt@xxxxxxxxxxxxxx> wrote:
> > > > In general, the kernel should report temperature readings exactly as
> > > > reported by the hardware. The cpu / gpu thermal driver works in 5 degree
> > > > increments,but we ought to do more accurate. The temperature will do
> > > > linear interpolation between the entries in the table.
> > > >
> > > > Test= $md5sum /dev/zero &
> > > > $while true; do grep "" /sys/class/thermal/thermal_zone[1-2]/temp;
> > > > sleep .5; done
> > > >
> > > > e.g. We can get the result as follows:
> > > >       /sys/class/thermal/thermal_zone1/temp:39994
> > > >       /sys/class/thermal/thermal_zone2/temp:39086
> > > >       /sys/class/thermal/thermal_zone1/temp:39994
> > > >       /sys/class/thermal/thermal_zone2/temp:39540
> > > >       /sys/class/thermal/thermal_zone1/temp:39540
> > > >       /sys/class/thermal/thermal_zone2/temp:39540
> > > >       /sys/class/thermal/thermal_zone1/temp:39540
> > > >       /sys/class/thermal/thermal_zone2/temp:39994
> > > >
> > > > Signed-off-by: Caesar Wang <wxt@xxxxxxxxxxxxxx>
> > > > Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> > > >
> > > > ---
> > > >
> > > > Changes in v3:
> > > > Suggested-by Daniel Kurtz,
> > > > the check doesn't reject "code == 0xfff"
> > > > Fixed in rk_tsadcv2_code_to_temp(u32 code)
> > > >
> > > > Changes in v2:
> > > > Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> > > >
> > > >    drivers/thermal/rockchip_thermal.c | 32
> > > > ++++++++++++++++++++++----------
> > > >    1 file changed, 22 insertions(+), 10 deletions(-)
> > > >
> > > > diff --git a/drivers/thermal/rockchip_thermal.c
> > > > b/drivers/thermal/rockchip_thermal.c
> > > > index 1bcddfc..ce18007 100644
> > > > --- a/drivers/thermal/rockchip_thermal.c
> > > > +++ b/drivers/thermal/rockchip_thermal.c
> > > > @@ -193,19 +193,22 @@ static u32 rk_tsadcv2_temp_to_code(long temp)
> > > >
> > > >    static long rk_tsadcv2_code_to_temp(u32 code)
> > > >    {
> > > > -       int high, low, mid;
> > > > -
> > > > -       low = 0;
> > > > -       high = ARRAY_SIZE(v2_code_table) - 1;
> > > > -       mid = (high + low) / 2;
> > > > +       unsigned int low = 0;
> > > > +       unsigned int high = ARRAY_SIZE(v2_code_table) - 1;
> > > > +       unsigned int mid = (low + high) / 2;
> > > > +       unsigned int num;
> > > > +       unsigned long denom;
> > > >
> > > > +       /* No code available, return callback */
> > > >           if (code > v2_code_table[low].code || code <
> > > > v2_code_table[high].code)
> > > > -               return 125000; /* No code available, return max
> > > > temperature */
> > > > +               return rk_tsadcv2_code_to_temp(code);
> > > Isn't this an infinite recursion?
> >
> > No, I think we can try check if it  is happened.
> > Maybe we can return a warning/error for it.
> I mean, if the 'if' condition is true, then this will just call the
> same function again with the same code, and again, and again...
> Just return an error code here, -ENOENT maybe?
> I am not sure what error code is appropriate.

Maybe "return -EAGAIN"
> > > >           while (low <= high) {
> > > > -               if (code >= v2_code_table[mid].code && code <
> > > > -                   v2_code_table[mid - 1].code)
> > > > -                       return v2_code_table[mid].temp;
> > > > +               if (code >= v2_code_table[mid].code &&
> > > > +                   code < v2_code_table[mid - 1].code)
> > > > +                       break;
> > > > +               else if (code == TSADCV2_DATA_MASK)
> > > > +                       break;
> > > >                   else if (code < v2_code_table[mid].code)
> > > >                           low = mid + 1;
> > > >                   else
> > > > @@ -213,7 +216,16 @@ static long rk_tsadcv2_code_to_temp(u32 code)
> > > >                   mid = (low + high) / 2;
> > > >           }
> > > >
> > > > -       return 125000;
> > > > +       /*
> > > > +        * The 5C granularity provided by the table is too much. Let's
> > > > +        * assume that the relationship between sensor readings and
> > > > +        * temperature between 2 table entries is linear and interpolate
> > > > +        * to produce less granular result.
> > > > +        */
> > > > +       num = v2_code_table[mid].temp - v2_code_table[mid - 1].temp;
> > > > +       num *= v2_code_table[mid - 1].code - code;
> > > > +       denom = v2_code_table[mid - 1].code - v2_code_table[mid].code;
> > > > +       return v2_code_table[mid - 1].temp + (num / denom);
> > > >    }
> > > >
> > > >    /**
> > > > --
> > > > 1.9.1
> > --
> > Best regards
> > Caesar Wang (çæè)
> > çåçèåçåæéåå
> > Fuzhou Rockchip Electronics Co.Ltd
> > çåççååéçèèäåé89åèäåAå18åæ(350003)
> > Addr:No.18 Building, A District, No.89, software Boulevard Fuzhou,
> > Fujian,PRC
> > Email:wxt@xxxxxxxxxxxxxx
> > Tel:+86-591-83991906/07->8221
> _______________________________________________
> Linux-rockchip mailing list
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